An experimental setup was developed for time-gated (nanosecond) fluorescence spectroscopy and imaging of microscopic samples. This makes it possible to depict individual components of complex fluorophores and to measure specific metabolites on the basis of their decay times. The field of applications includes the selective detection of intrinsic fluorophores and of photosensitizers in single cells, skin, and teeth, as well as of photosynthetic pigments in plants under various stress conditions.